つつもEven while ~ing, Even though ~ing, Despite ~ing, Although ~ing

Both express contrast between expectation and reality. つつ(も) implies that an action continues over time while another, opposing reality exists, as in 危険だと知りつつも挑戦した (I knew it was dangerous, yet I tried). ものの simply means although/even though, without emphasizing continuation, as in 雨は降ったものの試合は行われた (It rained, but the game was held).

Both くせに and つつ(も) express contradiction, but differ in tone. くせに is a casual expression with a blaming or critical tone, e.g. 知っているくせに何で教えてくれないの？ ('You know, so why won't you tell me!?'). つつ(も) is neutral and used to describe conflicting simultaneous actions, e.g. 危険だと知りつつも行った ('I went despite knowing at the same time that it was dangerous.').

Both mean 'while' or 'although' and are often interchangeable, e.g. '何度も休みつつ、ゴールまでたどりついた' ('While/although resting many times, I neared the goal'). This could also be expressed as '何度も休みながらも...'. However, ながらも requires the action to occur over time, so '手紙を開きつつ' ('while opening the letter') would typically not use ながらも.